1. Field of the Invention
This invention relates to a method for controlling an electrically operated pressing tool apparatus for pressing coupling elements with a clamping pincer. This invention also relates to a pressing tool apparatus used according to the method of this invention.
2. Description of Related Art
Pressing tool apparatus of the above mentioned type are used for pressing coupling elements, such as press sleeves, press fittings, connecting sleeves, and tube sections which are inserted into one another. The pressing tool apparatus includes a clamping pincer with clamping jaws which form a pressing space for receiving the coupling element to be pressed. The pressing pressure required for the pressing can be delivered by a hydraulic drive.
After each pressing, the pressing tool should be checked whether the coupling element has been pressed to the desired extent or whether the pressing force was too great or too small. The testing is visibly controlled. If the degree of the pressing is only just outside the tolerance limit, then it is difficult to visibly recognize. Furthermore the visual control depends on the reliability of the worker.
A pressing tool apparatus is a working apparatus which has an increased accident risk. Already, many accidents have occurred at work because the pincers are accelerated away in an uncontrolled manner and the fork-like receiver is spread open and deformed.
Therefore according to European Patent Reference EP-A 0 712 696, a monitoring element monitors the connection bolt in its completely inserted position and via a switch element is in connection with the drive motor.
Also when the clamping pincer is correctly held in the pressing tool apparatus, this alone still does not ensure a perfect pressing of the tubular workpiece. Reasons for the qualitatively unsatisfactory pressings may be very varied. Apart from reasons which are connected to the function of the pressing tool apparatus, other reasons are considered which are related to the inadequate machining. For example, the clamping pincer and its clamping jaws may become dirty, and thus a sufficient closure of the clamping pincer is not achieved or the dimensioning of the applied connecting sleeve or pressing sleeve does not correspond to the dimension which is envisaged for the corresponding pincer.
For these reasons, according to European Patent Reference EP-A 0 858 850, there is known a pressing tool apparatus with which the applied pressing pressure is determined and it is ascertained whether this pressing pressure lies within the predefined tolerance limits. Thus, a full closure of the clamping pincer is achieved. So that a monitoring may be effected correctly, the pressing tool apparatus must recognize which clamping pincer is operative. Such a clamping pincer recognition requires an electronic data exchange between the clamping pincer and the pressing tool apparatus, as well as an electronic logic through which the information may be evaluated to suitable signals which indicate a correct or incorrect pressing. Such electronic monitoring may then, without problem, be combined with further electronic information which also displays the correct actuation and the perfect operating condition of the pressing tool apparatus.
Since these pressing tools are often used on building sites, it is difficult to not dirty the clamping pincer. Such contamination then often leads to interruptions of the electronic transfer and thus to erroneous information.
Finally there is also known a pressing tool apparatus, for example from German Patent Reference DE-A 19 631 019, wherein an end pressing position of the pressing jaws is monitored. Accordingly the clamping pincers perceive this end pressing position and convey a signal to a display means. Also here an information transfer from the clamping pincer to the pressing tool apparatus must be effected. Also, suitable electronics must be integrated into the clamping jaws to likewise sensitive mechanical elements.
According to known art, information must be delivered from the clamping pincer to the pressing tool apparatus. It is thus one object of this invention to provide a method which does not require electrical or electronic data communication from the clamping pincer to the pressing tool apparatus but which itself procures this information.
This object is achieved with a method and an apparatus described in this specification and in the claims.
It is another object of this invention to provide a pressing tool apparatus which may function according to the method according to this invention. This object is achieved by a pressing tool apparatus with the features described in this specification and in the claims.